Thermoimaging process utilizing a photochromic material containing a spiropyran, a polyhalogenated hydrocarbon, a thiol compound and a polyvinylcarbazole

ABSTRACT

A process for forming a dye image comprising the image-wise heating in the presence of minor amounts of visible light of a recording material containing an intimate mixture comprising: 1. AT LEAST ONE SPIROPYRAN COMPOUND, 2. AT LEAST ONE ULTRAVIOLET-RADIATION SENSITIVE COMPOUND CAPABLE OF PRODUCING ON EXPOSURE TO ULTRAVIOLET-RADIATION WITH THE SPIROPYRAN COMPOUND A DYE SALT, AND IN WORKING RELATIONSHIP WITH SAID MIXTURE A COMPOUND OR MIXTURE OF COMPOUNDS BELONGING TO ONE OF THE FOLLOWING CLASSES. A. AN ORGANIC NITROGEN-CONTAINING COMPOUND COMPRISING A THIOL GROUP OR IN ITS TAUTOMERIC FORM A THIONE GROUP AS REPRESENTED IN THE FOLLOWING TAUTOMERIC STRUCTURAL PARTS:   B. A POLYMER CONTAINING N-vinylcarbazole units.

United States Patent Van den Houte et al. 1 June 3, I975 [54]THERMOIMAGING PROCESS UTILIZING A 3,785,820 [H974 lnouo: ct al .1 96/90PC PHOTOCHROMIC MATERIAL 3 8l0.762 5/l974 Laridon et al. t 96/90 RCONTAINING A SPIROPYRAN A 3.820.995 6/l974 Mertens et a]. 96/90 RPOLYHALOGENATED HYDROCARBON, A FOREIGN PATENTS OR APPLICATIONS THIOLCOMPOUND AND A 1,274,655 8/l968 Germany 96/90 PC POLYVINYLCARBAZOLEPrimary ExaminerWon Hv Louie, Jr. lnvenmrs' 'ggi z g yg zf gf ztAttorney, Agent, or FirrrlWilliam J. Daniel Royen, Wommelgem; Hugo VitalVan Goethem, Edegem; Edwin {57] ABSTRACT H d ik fl b h, M h l ll Aprocess for forming a dye image comprising the imf B l i age-wiseheating in the presence of minor amounts of visible li ht of a recordinmaterial containin an inti- [73] Ass1gnee: Agfa-Gevaert, Mortsel,Belgium mate miiwm comprising? g [22] Filed: June 25, 1973 l. at leastone spiropyran compound,

2. at least one ultraviolet-radiation sensitive [21] Appl. No.: 372,938compound capable of producing on exposure to ultravioletradiation withthe spiropyran [30] Foreign A lieation Priorit Data compound a dye salt,and in working relationship June 26 1972 United Kingdom 29915 72 willsaid mixture 3 Compound mixwm of compounds belonging to one of thefollowing 521 US. Cl 250/316; 96/27 R; 96/48 R; classes' R; a. anorganic mtrogen-contalnmg compound 51 1m. 61. G031: 5/04; G030 1/52comprising 3 thiol group or taummefic 581 Field of Search... 96/27 R, 48R, 48 OP, 90 R, form mime group as represented in the 96/90 250/3) 3nfollowing tautomeric structural parts:

[56] References Cited s:

UNITED STATES PATENTS be a polymer containing N-vinylcarbazole units.aum .1 3.642.479 2 1972 Van Allen et al. 96/90 PC 15 Claims, 2 DrawingFigures THERMOIMAGING PROCESS UTILIZING A PHOTOCIIROMIC MATERIALCONTAINING A SPIROPYRAN, A POLYIIALOGENATEI) HYDROCARBON, A THIOLCOMPOUND AND A POLYVINYLCARBAZOLE This invention relates tothermographic recording. The Belgian Pat. No. 771,848 relates to aphotographic process, wherein a recording material, containing anintimate mixture comprising 1. at least one spiropyran compound,

2. at least one ultraviolet-sensitive compound capable of producing onexposure to ultra-violet radiation with the spiropyran compound a dyesalt, and in working relationship with said mixture one or morecompounds belonging to one of the following classes:

A. polycyclic aromatic compounds,

B. aromatic carbonyl compounds,

C. organic compounds containing two radicals of differentelectron-affinity, the term radical including group and atom, linked toeach other through a conjugated system.

D. organic compounds containing an aromatic nucleus or aromatic ringsystem in which two adjacent carbon atoms are common to said nucleus orring system and to an adjacent ring that has no conjugated character andat one end is linked to the aromatic nucleus or ring system through acarboncarbon bond and at the other end linked to said nucleus or ringsystem through an electron-donating group, said organic compoundsincluding those having a said nucleus or ring system in substitutedform,

E. polymeric compounds containing recurring units of the followinggeneral formula:

wherein:

Z represents sulphur or a single bond.

A represents a single bond or a divalent hydrocarbon group.

each of R, and R represents hydrogen or a lower alkyl radical,

each of Q. and O represents hydrogen or to gether represent thenecessary atoms to cclose an adjacent carbocyclic nucleus including asubstituted adjacent carhocyclic nucleus,

each of Q and represents hydrogen or together represent the necessaryatoms to close an adjacent carbocyclic nucleus including a substitutedadjacent carbocyelic nucleus, and

n represents 1 or 2,

F. organic nitrogen-containing compounds having a thiol group or intheir tautomeric form a thione group as represented in the followingtautomeric structural parts:

HS J

G. inorganic compounds producing photoelectrons under the influence ofactivating electromagnetic radiation and having a basic or amphotericcharacter,

exposed information-wise to activating electromag netic radiation of adose being sufficient to bring about a directly visible image.

The United Kingdom Patent Application No. 40,349/71 being a modificationof the United Kingdom Patent Application No. 4] ,749/70, whichcorresponds with the above-mentioned Belgian Pat. No. 771,848 relates tothe use of an amide, acylamino or ureido compound in a photographicprocess operating with said spiropyran and ultraviolet-sensitivecompound. The amido, acylamino, or ureido compound used in admixturewith said spiropyran compound and ultraviolet-sensitive compoundcorresponds to the following general formula:

wherein:

R represents an organic group, e.g. of the type present in a carboxylicacid chloride, e.g. an alkyl group, an aryl group, or heterocyclic groupincluding these groups in substituted form, or a NHR or group, in whicheach of R and R represents an alkyl group or an aryl group, e.g. aphenyl group including these groups in substituted form, and

R represents hydrogen or an organic group as is di rectly linked to theNH; group of an organic amino compound, e.g. an alkyl group, an arylgroup, or a heterocyclic group including these groups in substitutedform.

It has now been found that recording materials de scribed in the abovementioned United Kingdom Patent Application No 40,349/71 and in theBelgian Pat. No. 771,848 having in the recording layer composition anorganic nitrogen-containing compound comprising a thiol group or in itstautomeric form a thione group as represented in the followingtautomeric structural parts:

According to a preferred recording embodiment of the present inventionthe recording material is exposed with infrared radiation and a minoramount of visible light while being in heat-conductive contact with anoriginal containing infrared-absorbing image markings. The exposure ispreferably reflectographical i.e. the in frared radiation is allowed topass first through the recording material before it strikes theoriginal. Accord ing to this embodiment the infraredabsorbing imagemarkings of the original are heated and the heat gener ated in thesemarkings is transmitted by conduction to the recording layer. Theinfrared-absorbing image markings are. e.g.. printed characters the inkof which contains carbon black or a metallic compound.

Two possible ways of effecting reflectographic exposure are illustratedin the accompanying FIG. 1 and HO. 2.

According to the reflectographic exposure technique of FIG. 1 aphotosensitive material 1 comprising a photo-sensitive layer 2 appliedto a support 3, which is capable of transmitting infrared radiation andvisible light is placed between the infrared radiation source 4 and theoriginal 5 bearing infra-red-absorbing indicia 6, during the exposure.

According to the reflectographic exposure technique of FIG. 2 thephotosensitive layer 7 of the photosensitive material 12 is facing theinfrared radiation source 8. During exposure the support 9 of thephotosensitive layer 7 is in contact with the infrared-absorbing indicia10 of the original 11. The support 9 of the photosensitive layer 7 isthin and heatconducting. In both exposure arrangements the infraredexposure source emits infra-red radiation and a minor amount. e.g. up topercent of visible light.

Spiropyran compounds suited for photothermographic image formationaccording to the present invention are spiropyrans containing at leastone pyran ring having in the orthoand meta-position to the oxygen atom acondensed benzo. naphtho, or other higher aromatic polycyclic condensedring system including these condensed rings or ring systems insubstituted form, e.g. an anthraceno or a phenanthreno ring system as ispresent e.g. in a spirodibenzopyran, a spirodinaphthopyran, aspirobenzonaphthopyran. a 1.- 3.3-trimethylindolinobenzospiropyran. a1.3.3- trimethyLindolinonaphthospiropyran or such spiropyrans containingcondensed aromatic nuclei of the anthracene or phenanthrene type.

In said spiropyrans the pyran rings, the condensed benzo. the condensedhigher aromatic rings as well as the l.3.3 trimeth vlindolino ring maybe substituted.

Suitable substituents therefor are, erg. hydrocarbon groups such asalkyl groups, e.g. lower alkyl groups such as methyl. substituted alkylgroups. e.g. substituted with halogen. or phenylsubstituted alkylgroups. alkylene ester groups e.g. -CH COOC H alkylene carboxyl groupse.g. CH COOH, carbonamide groups or substituted carbonamide groups e.g.

ONE-Q! halogen. nitro, hydroxy. alkoxy. aryloxy or a substituent linkingthe carbon atoms in 3.3'-position in the spiropyran system together.e.g. a (CH-fl -chain wherein n is 2 or 3.

General formulae covering particularly suited spiropyrans are thefollowing:

-CONH- Q or R and R, together represent a -(CH chain wherein n =2. or 3to link the carbon atoms in the 3 and 3' positions together.

Suitable spiropyran compounds and their preparation are described in thepublihsed German Pat. Nos. 1,274,655 filed Dec. 15, 1965 by TelefunkenPatentverwertungs G.m.b.H., 1,269,665 1,286,110

1,286,111 and 1.286112 all filed Sept. 30 1966 by 5 TelefunkenPatentverwertungs G.m.h.H., and by W Dilthey, Berres Holterkoff, Wubken..l. Prakt. Chem. [2] 114, 187 (1926). by C. F. Koelsch and W R, Workmanin J. Am. Chem Soc. 74 6288 (1952) and by l. M. Heilbron and G. F.Howard in J. Chem. Soc. {1934),1571.

Preferred spiropyran compounds are spirodinaphthopyrans andspirobenzonaphthopyrzins including such compounds wherein thenaphthoand/or benzo ring(s) is (are) substituted.

An illustrative list of particularly useful spiropyran compounds isgiven in the following Table l.

Spi ropyran c ompound Melting point CtgTbQQ Ci 5Q Gil -COOK CHZ-CO-NH- QTable 1 Continued Spiropyran compound Melting point 0 Table 1 ContinuedSpiropyran compound Melting point Table l Continued Spiropyran compoundMelting point in order to illustrate the preparation of the diarylospiropyran and the indolino-arylospiropyran compounds, more detailedly,the following preparations are 1 given:

PREPARATION 1 condenser and a gas inlet tube reaching nearly the bottomof the flask are introduced:

ethanol l litre hutanunc 22 ml (0.35 mole) Z-hydroxy-lnaphthaldehydc 86g (0.5 mole) The flask is shaken until partial dissolution of theingredients. Dry dydrogen chloride gas is introduced at a rate. whichallows complete absorption and the start of ethanol reflux. Thereuponthe already highly blue mixture is cooled in a mixture of ice and sodiumchlo ride and the introduction of hydrogen chloride gas continued untilsaturation. ln the reaction mixture green crystals of pyrylium salt areformed and the crystallization is allowed to proceed overnight in arefrigerator.

The pyrylium salt formed is separated by suction, washed with ethanoland thereupon brought into sus pension in 300 ml of ethanol.

A l0 percent by weight aqueous solution of ammonium hydroxide is addedwith stirring until the mixture is definitely alcaline. During thisoperation the mixture becomes colourless.

The obtained crystalline product is separated by suc tion, washed withwater, and dried.

Finally the spiropyran compound is recrystallized from 600 ml of benzeneand again separated and dried under reduced pressure at SO-60C. Yield:45 g. Melting point: 204C.

PREPARATlON 2 In a 100 ml flask fitted with a reflux condenser thefollowing ingredients are introduced:

salicylaldchy dc lJJ-trimeth l-Z-mcth lcnc indnlcnine ethanol 3.7 g(0.03 mole) The solution is refluxed for 2 h. Thereupon the mixture iscooled and filtered. To the filtrate water is added so that a solidproduct precipitates. which is separated by suction, washed with water,and dried under vacuum conditions. The spiran compound is recrystallizedfrom 15 ml of hexane.

Yield: 5 g. Melting point 9394C.

The compound capable of producing a dye salt with a spiropyran onexposure to activating electromagnetic radiation, for use according tothe present invention is preferably an organic polyhalogen compound,from which a halogen-containing radical can be separated photolytically.Compounds posssessing that property are within the scope of thefollowing general formulazwherein:

each of A, B, X. and Y is a halogen atom of the group of chlorine.bromine or iodine, or

wherein one of said symbols A, B. X, or Y represents an alkyl group,including a substituted alkyl group, e.g. a halogen-substituted alkylgroup. a hydroxyalkyl group or an aralkyl group e.g. benzyl. an arylgroup, a substituted aryl group. or a heterocyclic group e.g. aquinoxaline or quinaldine group or an aroyl group and the other symbolsare chlorine. bromine or iodine, or wherein at least two of said symbolsA, B, X or Y represent an aromatic acyl group e.g. benzoyl and the othersymbols chlorine, bromine. or iodine.

Suitable representatives falling within the scope of that generalformula are organic halides such as carbon tetrabromide. bromoform.iodoform, hexachloroethane, hexabromoethane, pentabromoethane. l,l.2.2-tetrabromoethane, a.ma-tribromoacetophenone. and tribromoethanol.

The recording materials used according to the pres ent inventioncontaining a spirodiarylopyran compound and said thiol or thionecompound in combina tion with poly-N-vinylcarbazole have a remarkablyhigh sensitivity to white light and particularly to red light whenspectrally sensitized with acetanilide or acetanilide derivatives.

Specific exampless of such useful sensitizing agents are listed in thefollowing table 2.

Table 2 Continued Number of the c omp ound Structural formula MeltingReference for point preparation 1 fiU-NH-COCH 242 L-Vogel,

Practical Organic Chemistry, Longmans, Green and Co. Ltd., London, 5rdEd., p. 646

152 J.C'hem.Soc.

The amount of spectral sensitizing agent may vary within a wide rangedepending on the intensity of the effect desired.

Preferred amounts of sensitizing agent are in the weight ratio range of1:1 to 0.05:1 with respect to the spiropyran compound(s).

Preferred thiol and thione compounds correspond to the followingtautomeric structures:

wherein:

and

Z represents the necessary atoms to close a 5- or 6- memberedheterocyclic nitrogen-containing ring or X represents oxygen, sulphur,selenium or the group in which R is hydrogen or an organic group, e. g.an alkyl group including a substituted alkyl group. preferably a C -Calkyl group'or an aryl group.

ring system including such ring or ring system in .1 substituted forme.g. a benzothiazole, benzoselen- 0-5 azole, benzoxazole orbenzimidazole ring. Z Particularly useful thiol and thione compounds arelisted in the following table 3.

ll vimber Structural formula. Melting Reference for or the pointpreparation compound C g 505 Org. 1711.2,

S 2 6/ \-BH J.Am.Chem-Soc.

L l {& 1+2. (1927) 0 3 --BK 192 Org.87nth. 5

Table 3-Continued Number Structural formula Melting Reference for of thepoint preparatlon compound r I H 210 J.Prakt-Chem.

s lgzg, 52, 12s it C 5 g '15; Ber-55, 1295 9 N s=c N I u HN--N Usefulimage results are obtained in the process of the present invention withsaid thiol or thione compounds in a weight ratio of at least 1:30 to l:]with respect to the spiropyran compound. The N vinylcarbazole polymer orcopolymer is preferably used as binding agent so that it is present in alarge molar excess with respect to the spiropyran compound.

The spiropyran compoundts) is (are) preferably used in admixture with a5- to -fold amount by weight of photosensitive organic halogen compoundsuch as Carbon tetrabromide.

This ratio, however, is not limitative since useful results are obtainedwith, e.g., the spiropyran and photosensitive polyhalogen compound in aratio by weight in the range of 1:1 to 1:50.

In order to diminish the rate of spontaneous thermal colour formationover long periods of time as might be encountered during storage of therecording material and its processing, so-called anti-foggants may beadded to the photosensitive composition. Suitable antifoggants includetriaryl compounds of group V ele merits, e.g. triphenylstibine andsterically hindered phenols, e.g. 2,6-di-terLbutyl-p-cresol and otherreducing agents or compounds accepting atmospheric oxygen.Triphenylstibine and analogous compounds for the purpose of the presentinvention are described in the United Kingdom Pat. No. l,O7l,l04.

Preferred amounts of anti-foggant agent such as triphenylstibine arewithin the weight ratio range of 1:100 to 10:100 with respect tophotosensitive carbontetra bromide and/or iodoform.

A dry photographic coating containing the above mentioned ingredientsmay be formed by dissolving the binding agenttsl in a suitable inertsolvent that acts as dispersing or dissolving medium for the otheringredients and that is removed from the coating composition byevaporation so that a solid photographic recording layer is left on aproperly chosen support. The supports may be of any kind encountered insilver halide photographic materials, e.g. paper and film supports.

In order to realize the highest sensitivity it is desirable to coat therecording layers in the absence of oxygen or to keep them in anoxygen-free environment before the exposure.

For that purpose hydrophobic polymers are used preferably as bindingagent. They shield the ingredients from a direct contact with theatmosphere and more especially from oxygen as much as possible.

Particularly suitable binders for use in the present invention arehydrophobic polymers and copolymers containing, e.g. styrene, vinylacetate, acrylonitrile, acrylate, methacrylate, Nw'inylcarbazole orbutadiene units, hydrophobic cellulose derivatives, phenoxy resins orpolycondensates of the polyester type, eg. polycarbonates.

When no selfsupporting layer is produced these polymers may be used inadmixture for improvement of the mechanical strength or adhering powerof the recording layer to its subbed or non-subbed support.

Suitable subbing layers for photochromic layers containing a spiropyrancompound are described in the Belgian Pat. No. 782,026. Said subbinglayers applied to a polyester film support are made of a partiallysaponified copolymer of vinyl chloride and vinyl acetate and/or of apolymer or copolymer of acrylic or methacrylic acid esters of aliphaticor cycloaliphatic alcohols containing from 1 to 8 carbon atoms.

It has been established experimentally that the adherence of recordinglayers containing poly-N- vinylcarbazole or copolymers containing N-vinylcarbazole units to polyester resin supports can be markedlyimproved by using in admixture with the N- vinylcarbazole polymer orcopolymer a polyester, a phenoxy resin or a phenol-formaldehyde resin. Apreferably applied polyester resin is polyethylene isophthal ate.

A preferred phenoxy resin is EPONOL 55-8-40 of Shell, the Netherlands.

Suited phenolformaldehyde resins are: the polycondensatinn product of amixture of p-cresol and phenol with formaldehyde (50:50), thepolycondensation product of a mixture of ptert.butylphenol and phenolwith formaldehyde, the polycondensation product of p-cresol andformaldehyde (used in excess) 2 xylenol-formaldehyde resin like RESlN Rof Brit ish Resin Products. Great-Britain.

The resins improving the adherence are preferably used in a percentageby weight calculated on the re cording layer of at least 3 percent.

The infrared exposure of the recording materials used according to thepresent invention may proceed in any known thermographic copyingapparatus of the reflectographic type. A suitable operating temperatureis in the range of 90 to 150C.

The recording materials are suited to produce coloured copies ofimage-wise infrared-absorbing originals, the colour of the dye-imagebeing determined by the type of spiropyran compound used.

The prints obtained may be stabilized by washing out the residual freeradical generator with a suitable solvent or solvent mixture, e.g. ahydrocarbon liguid such as petroleum ether optionally mixed withacetone, or by simply evaporating the free radical generator by raisingthe temperature if the compound involved is sufficiently volatile. Forthe latter purpose carbon tetrabromide having a high photosensitivity ora mixture of carbon tetrabromide and iodoform is preferred as freeradical generator.

According to a preferred embodiment the stabilization proceeds withincreased speed when the recording layer is first overall heated atabout 80C in the absence of visible light for at least 5 sec. and thentreated with a chlorinated solvent, e.g. perchloroethylene at roomtemperature (C) for at least l5 sec in order to extract thephotosensitive polyhalogen compound.

Stabilization may proceed very fast by dipping the exposed recordingmaterial in a heated organic liquid having a relatively high boilingpoint, preferably above 200C and not affecting the recording layer. Theorganic liquid is preferably heated in the range of 145 to 165C and thedipping time is e.g. 5 to 20 sec.

Suitable liquids are mineral oil of aliphatic or naph' thenic naturee.g. motor oil and lSOPAR G (trade name). A post-treatment with asolvent, e.g. a chlorinated hydrocarbon solvent may be necessary toremove the residual oil film.

The present invention is illustrated by the following examples. Thepercentages are by weight unless otherwise indicated.

EXAMPLE 1 A photosensitive composition consisting of:

0.12 g of carbon tetrabromide 0.12 g of iodoform 0.1 g of3-methyl-di-B-naphtho-spiropyran 0.03 g of triphenylstibine 0.06 g ofacetanilide and 8 ml of a 5 percent solution of poly-N-vinylcarbazole inmethylene chloride,

was applied to a non-subbed polyethylene terephthalate support in athickness of 0.12 mm. The layer was dried at room temperature.

The photosensitive film obtained was exposed reflectographically in a 3MThermofax copying machine (Model 47) in contact with an opaque originalbeing a black printed text on white paper. A dense blue positive imageof the original was obtained.

The copy as such was not stable to light and had to be stabilized byheating at 170C.

EXAMPLE 2 A same photosensitive composition as in example 1 was used,with the difference, however, that 0.06 g of compound having thefollowing formula:

was substituted for 0.06 g of acetanilide. A same thermographic exposurestep as in example l was executed.

Positive blue images showing no fog were obtained. Fixation of the imageagainst any further action of light had to be executed by heating at170C.

EXAMPLE 3 A photosensitive composition consisting of:

0. l 5 g of carbon tetrabromide 0. l 5 g of iodoform 0.04 g ofdi-B-naphthospiropyran 0.01 g of 2-mercaptobenzothiazole 0.025 g oftriphenylstibine, and

10 ml of 5 percent solution of poly-N-vinylcarbazole in methylenechloride,

was applied to a non-subbed polyethylene terephthalate support in athickness of 0. 1 2 mm. Drying was done at 50C.

The same circumstances of exposure as in example 1 yielded a positiveblue copy of the original. A very faintly fogged background was formed.Stabilisation of the image against light was also achieved by a thermaltreatment at l-l C.

EXAMPLE 4 A photosensitive composition consisting of:

200 ml of 5 percent solution of poly-N-vinylcarbazole in a mixture ofmethylene chloride and trichloroethane (3:1)

2.5 g of carbon tetrabromide 2.5 g of iodoform 2.5 g oftrimethyldi-B-naphthospiropyran 0.8 g of triphenylstibine, and

0.2 g of 2-mercaptobenzothiazole EXAMPLE 5 Same compositions asmentioned in example 4 were produced with the difference, however, thatother spiropyran compounds were used, viz. compounds 4, 9, I5, 22 and 26of Table l yielding blue, magenta, yellow and cyan images respectively.

EXAMPLE 6 A photosensitive composition consisting of:

0.15 g of carbon tetrabromide 0.05 g of iodoform 0.1 g of3-methyl-di-B-naphthospiropyran 0.01 g of 2-mercaptobenzothiazole, and

10 ml of a percent solution of polystyrene in a mixture of methylenechloride and trichloroethylene 1:1 1

was applied in a thickness ofO. l 2 mm to a non-subbed polyethyleneterephthalate support. The layer was dried at room temperature.

Reflectographic exposure proceeded according to the arrangement of FIG.1 in a 3M Thermofax photo copier. model secretary, set at the lowesttransport speed and yielded a very dense positive reproduction of theoriginal.

EXAMPLE 7 A photosensitive composition consisting of:

0.12 g of carbon tetrabromide 0.12 g of iodoform 0.16 g of3-methyl-di-B-naphthospiropyran 0.04 g of triphenylstibine 0.01 g ofZ-mercaptobenzothiazole, and

ml of a 5 solution of poly-N-vinylcarbazole in a mixture of methylenechloride and trichloroethane 1:1)

was applied in a thickness of 0.12 mm on tracing paper. The film wasdried at 50C.

Reflectographic exposure in a 3M Thermofax Dry Photocopier model 47(medium speed), according to the arrangement indicated in FIG. 2 yieldeda directly legible positive image.

EXAMPLE 8 EXAMPLE 9 To a photosensitive composition containing:

0.12 g of carbon tetrabromide 0.12 g of iodoform 0.1 g of3-methyl-di-Bmaphthospiropyran 0.03 g of triphenylstibine 0.06 g ofacetanilide. and

8 ml of a 5 solution of poly-N-vinylcarbazole in a mixture of methylenechloride and dichloroethane (50:50).

were added 0.50 g of a 4 71 solution of polyethylene isophthalate inmethylene chloride. The mixture obtained was coated on a polyethyleneterephthalate support in such a way that after drying at 40C a layer of0. l 2 mm was obtained.

The material obtained was exposed and processed as described inExample 1. A deep blue image in a very good adhering scratch-resistantrecording layer was obtained.

The same good results were obtained by replacing the polyethyleneisophthalate respectively by:

RESIN R (trade name of British Resin Products.

Great Britain. for a xylenol-formaldehyde resin) it copolycondensate ofp-cresol and phenol with formaldehyde (50/50) a polycondensate ofp-cresol and formaldehyde a copolycondensate of p-tert.butyl-phenol andphenol with formaldehyde.

EXAMPLE 10 A photosensitive composition consisting of:

0.12 g of carbon tetrabromide 0.12 g of iodoform 0.1 g of3-methyl-di-Bmaphthospiropyran 0.035 g of triphenylstibine 0.060 g ofacetanilide 0.50 g of a 4 7c solution of polyethylene isophthalate inmethylene chloride, and

8 ml of a 5 solution of poly-N-vinylcarbazole in a mixture of methylenechloride and dichloroethane (50:50l

was coated on a polyethylene terephthalate support in such a way thatafter drying at 40C a layer of 0. 1 2 mm was obtained.

The material obtained was exposed as described in Example 1.

The stabilization of the image proceeded according to one embodiment byheating the recording layer whilst pressing it for 10 sec. in contactwith a metal rol ler heated at C. Subsequently, the recording materialwas dipped for 15 sec at room temperature (20C) into perchloroethylene.The image thus obtained was stable to daylight and had an opticaldensity of 1.80.

The stabilization could equally well be effected according to a secondembodiment by dipping the exposed material for 5 sec. in lSOPAR G (tradename of Shell Company. the Netherlands. for a mixture of hydrocarbonsboiling in the range of 166-170C) heated at C.

The recording layer containing the stabilized image wasscratch-resistant and strongly adhered to its support.

The N-vinyl polymers and copolymers containing N- vinylcarbazole unitswhich can be used according to the invention can be prepared byapplication of one of the various known polymerization procedures, e.g.,by pearlor emulsion polymerization or by polymerization in solution. Theinitiation of the polymerization can occur by free radicals, by ionformation, or by radiation e.g., with actinic light. The polymerizationdegree is not critical and may vary between wide limits. As far as thecopolymers are concerned the content of groups corresponding to thegeneral formula given hereinbefore is not critical and. as shownhereinafter in the table of copolymers containing N-vinylcarbazoleunits. it may vary between wide limits, e.g. between 20 and 95 percent.in accordance with the desired properties of the compounds used in thepreparation of the copolymers and the required sensitizing and/ormechanical properties. In general, the best results are attained withcopolymers having a content of vinylcarbazole units between 40 and 90percent.

The preparation of suitable poly-N-vinylcarbazoles is described e.g. inthe German Pat. Nos. 931,731. 936,421. 1.097.680 and 1.158.367 and theUS. Pat. No. 2.072.465.

The preparation of suitable N-vinylcarbazole copolymers is described inthe United Kingdom Pat. No. 964.875. which specification also contains apreparation receipt for poly(N-allyl carbazole) (R 2 CH and R H) and forpoly(N-propenyl carbazole) (R. H. R H. A CH;).

Halogen-substituted poly-N-vinyl carbazoles are de scribed in thepublished Japanese Patent Applications 21.875/67, 25.230/67. 7.592/68.19.751/67 and 7.59l/68.

For illustrative purposes suitable vinyl copolymers containing N-vinylcarbazole units are enumerated in the following table 4.

Table 4 Copol mer mole "/1 of N-vinylcarhazole copolymer ofN-vinylcarbazolc and \inylidene chloride 85.4

copolyrner of N- inylcarbazole and 3.3.5-trimethyl 93 isononylethcrcopolymcr of N-vinylcarbazole and vinyl acetate 88.6

copolymer of N-vinylcarbazolc and isopropenyl acetate 94.5

copolymer of N-vinylcarbazole and vinylstearatc 37.5

copolymer of N'vinylcarbazole and methyl acrylate 67.6

copolymer of N-vinylcarbazole and ethyl acrylate 41 graft copolymer ofN-vinylcarbazole and ethyl-acrylate 911.3

emulsion polymer of Nviny'lcarb;i2t)le and 94.5 polyethylacryatecopolymer of N-vinylcarbamle and nbutyl acrylate 58.3

copolymer of N-vinylcarbazole and 2-ethyl 51.6 hexylacrylate copolymerof Nvinylcarbazole and 76.6 ucryloxyethyldiethylamine copolymer ofN-vinylearbazolc and vinylcinnamate 92.5 copolymer of Nvinylcarbavoleand methyl 62.7 methacrylate copolymer of N-vinylcarbazolc and isobutyl51.8 methacrylatc copolymer of Nvinylcarba7ole and lauryl rnethacrylatc77.4

copolymcr of N-vinylcarhazole and methylacryloxethyl 9.7 diethylaminecopolymer of Nwinylcarbazolc and acrylonitrilc 88 graft copolymer ofN'vinylcarba/ole and butylaldehyde 3U acetal of p0l)'\ln}ltlltjt1l10lcopolymcr of N-vinylcarbazole and 82.4 dit Idichloroethyl)-\inylphosphonatc copolymcr ot' N\ir|)lcarha/ole and styrene 49 graftcopolymcr ol' N-vinylcarbamlc and polystyrene 27.3

copol mcr of Nwinylcarhalolc and vinylnaphthalcne 47.1

copolymer of N-vinylcarhazolc and anthracene(9,lll) 91,5

copolymcr of N-vinylcarbamlc and 2-\'inylpyridine 31.8

28 Table 4-Continued Copolymer mole "/1 of N-viny learba/ole copolymcrof N-vinylcarbalolc and 4-\in vlpyridine copolymcr of N-\inylcarba7olcand N-\ inylp rrolidinc 69.1

graft copolymer of a tcrpolymcr of vinyl chloride. vinyl acetate. andmaleic anhydride with NAll'lXlLill'llitlOlC We claim:

1. A process for forming a dye image comprising applying a heat patternhaving a temperature of at least 90C of the image in the presence ofminor amounts of about up to 20% of visible light to a recordingmaterial including a recording layer containing an intimate mixturecomprising:

1. at least one spiropyran compound of the group consisting of aspirodibenzopyran. a spirodinaphthopyran. a spirobenzonaphthopyran, a1.3.3- trim ethylindolinobenzospiropyran. a 1.3.3-trimethylindoline-naphthospiropyran. or a spiropyran that contains acondensed aromatic nucleus of anthracene or phenanthrene. and

at least one ultraviolet radiation-sensitive polyhalogen compoundcapable of producing on exposure with ultra-violet radiation with thespiropyran compound a dye salt and having the general formula:

wherein: each of A. B. X and Y is a chlorine. bromine or iodine atom. orone of said groups A. B. X or Y is an alkyl group. an aryl group or anaroyl group and the other groups are each chlorine. bromine. or iodine.or two of said groups A. B. X or Y each is an aromatic acyl group andthe other groups chlorine. bromine. or iodine. and in working relationwith said mixture at least one of the following compounds.

a. a tautomeric organic nitrogen containing compound corresponding tothe following general formula:

in which: X represents oxygen. sulphur. selenium or the group in which Ris hydrogen. or an alkyl. allyl. or phenyl group. and

Z represent the necessary atoms to close a or 6- membered heterocyclicnitrogen-containing ring system, and b, a polymer containingN-vinylcarbazolc units.

2. A process according to claim I, wherein the pattern-wise heatingolthe recording material proceeds by exposure thereof to infraredradiation and a minor amount of visible light while said layer is inheatconductive contact with an original containing infra red-absorbingimage markings.

3. A process according to claim 2. wherein the expo sure to saidinfra-red radiation and visible light is a re flectographic exposure.

4. A process according to claim 3, wherein said layer is applied to asupport transparent for infrared radiation and visible light and saidexposure is made through said support.

5. A process according to claim 3, wherein said layer is applied to asupport that is heat-conductive and said exposure is made through saidlayer while said support is in contact with said original markings.

6. A process according to claim 1, wherein the polyhalogen compound iscarbon tetrabromidc.

7. A process according to claim 1, wherein the polymer containingNvinylcarbazole units is poly-N- vinylcarbazole serving as binding agentfor said layer.

8. A process according to claim I, wherein the layer contains also anamido, acylamino. or ureido compound.

9. A process according to claim 8, wherein said amido, acylamino orureido compound corresponds to the following general formula:

wherein:

R represents an organic residue of the type present in a carboxylic acidchloride, a l lHR or 12. The process of claim 1 wherein said spiropyrancompound corresponds to one of the general formulae:

R, R R',, R R R and R each represent hydrogen, alkyl, alkyl substitutedwith halogen, alkyl sub stituted with an ester group, alkyl substitutedwith a carboxyl group, alkyl substituted with a N- phenylcarbamyl group,a hydroxy group, an alkoxy group, an aryloxy group, a phenyl group,piperidyl, acetyl, halogen, nitro, or R, and R together represent a-(CH- chain wherein n 2 or 3 to link carbon atoms in the 3 and 3'positions together.

13. The process of claim 1 wherein said layer is pattern-wise heated toa temperature in the range of about -l50C.

14. The process of claim 1 wherein said nitrogen compound is used in aratio by weight of about l:30 to about lZl relative to said spiropyrancompound.

15. The process of claim 1 wherein said spiropyran compound is used in aratio of about l:5 to about l:50

relative to said polyhalogen compound

1. A PROCESS FOR FORMING A DYE IMAGE COMPRISING APPLYING A HEAT PATTERNHAVING A TEMPERATURE OF AT LEAST 90*C OF THE IMAGE IN THE PRESENCE OFMINOR AMOUNTS OF ABOUT UP TO 20% OF VISIBLE LIGHT TO A RECORDINGMATERIAL INCLUDING A RECORDING LAYER CONTAINING AN INTIMATE MIXTURECOMPRISING:
 1. AT LEAST ONE SPIROPYRAN COMPOUND OF THE GROUP CONSISTINGOF A SPIRODIBENZOPYRAN, A SPIRODINAPHTHOPYRAN, A SPIROBENZONAPHTHOPYRAN,A 1,3,3TRIMETHYLINDOLINOBENZOSPIRROPYRAN, A1,3,3TRIMETHYLINDOLINE-NAPHTHOSPIROPYRAN, OR A SPIROPYRAN THAT CONTAINSA CONDENSED AROMATIC NUCLEUS OF ANTHRACENE OR PHENANTHRENE, AND
 1. Aprocess for forming a dye image comprising applying a heat patternhaving a temperature of at least 90*C of the image in the presence ofminor amounts of about up to 20% of visible light to a recordingmaterial including a recording layer containing an intimate mixturecomprising:
 1. at least one spiropyran compound of the group consistingof a spirodibenzopyran, a spirodinaphthopyran, a spirobenzonaphthopyran,a 1,3,3-trimethylindolinobenzospiropyran, a1,3,3-trimethylindoline-naphthospiropyran, or a spiropyran that containsa condensed aromatic nucleus of anthracene or phenanthrene, and
 2. atleast one ultra-violet radiation-sensitive polyhalogen compound capableof producing on exposure with ultra-violet radiation with the spiropyrancompound a dye salt and having the general formula:
 2. AT LEAST ONEULTRA-VIOLET RADIATION-SENSITIVE POLYHALOGEN COMPOUND CAPABLE OFPRODUCING ON EXPOSURE WITH ULTRAVIOLET RADIATION WITH THE SPIROPYRANCOMPOUND A DYE SALT AND HAVING THE GENERAL FORMULA:
 2. A processaccording to claim 1, wherein the pattern-wise heating of the recordingmaterial proceeds by exposure thereof to infrared radiation and a minoramount of visible light while said layer is in heat-conductive contactwith an original containing infrared-absorbing image markings.
 3. Aprocess according to claim 2, wherein the exposure to said infra-redradiation and visible light is a reflectographic exposure.
 4. A processaccording to claim 3, wherein said layer is applied to a supporttransparent for infrared radiation and visible light and said exposureis made through said support.
 5. A process according to claim 3, whereinsaid layer is applied to a support that is heat-conductive and saidexposure is made through said layer while said support is in contactwith said original markings.
 6. A process according to claim 1, whereinthe polyhalogen compound is carbon tetrabromide.
 7. A process accordingto claim 1, wherein the polymer containing N-vinylcarbazole units ispoly-N-vinylcarbazole serving as binding agent for said layer.
 8. Aprocess according to claim 1, wherein the layer contains also an amido,acylamino, or ureido compound.
 9. A process according to claim 8,wherein said amido, acylamino or ureido compound corresponds to thefollowing general formula: R1-CO-NH-R2 wherein: R1 represents an organicresidue of the type present in a carboxylic acid chloride, a -NHR3 or10. A process according to claim 1, wherein the material ispreliminarily treated to stabilize the eventual dye image by uniformlyheating the recording layer in the absence of visible light at atemperature of about 80*C and then treating it with perchloroethylene atroom temperature.
 11. A process according to claim 1, wherein the dyeimage is stabilized by dipping the exposed recording material in aninert organic liquid heated between 145* and 165*C.
 12. The process ofclaim 1 wherein said spiropyran compound corresponds to one of thegeneral formulae:
 13. The process of claim 1 wherein said layer ispattern-wise heated to a temperature in the range of about 90*-150*C.14. The process of claim 1 wherein said nitrogen compound is used in aratio by weight of about 1:30 to about 1:1 relative to said spiropyrancompound.